What is Windrow Composting? Its Process, Advantages and Applications

Waste is a major problem in the world, in Kathmandu, organic waste amounts to almost 70% of the total waste. Another data shows that municipal solid waste currently stands at 1.3 million tons. This figure is expected to double in just over a decade. The caring for and management of global waste is a global concern for the Earth as the population of Earth grows, and places where waste is deposited becomes a problem. People are keeping looking for waste-to-energy and creative solutions for the world’s waste problems, among which composting becomes an effective method to solve the the problem of organic waste — food, leaves, palm oil waste, sugar press mud, biogas waste and manure etc. Commercial composting facility turns organic and biodegradable materials into compost to feed the soil at farms and residential and business landscaping projects.

As we all know, composting can take anywhere from several weeks to a year to complete depending on the method used. Here I would like to introduce WINDROW COMPOSTING–one of the most popular commercial composting technology worldwide.

Windrow Composting Advantages

◆ Windrow turning is important for speeding up the composting process because it breaks preferential air pathways, and brings the material from the outside to the center for pathogen kill.

◆ Windrow composting is a suitable option for manure management, reducing risks of odor, soil and water pollution.

◆ Composting significantly reduces the amount of organic material ending up landfills, taking the example of Commercial composting at the Iowa City Landfill, about 7,500 tons of organics each year—yard waste, leaves and some food waste are processed into high-quality compost whose quantity arrives to 2,100 tons.

◆ Windrow composting does require a large amount of land and the leachate produced does have the possibility to contaminate surface and ground water, but with proper infrastructure both of those concerns are easily handled.

Application of Windrow Composting Method

◆ Windrow composting is suitable for large volumes of organic waste generated by entire communities and collected by local governments, and food processing businesses (e.g., restaurants, cafeterias, packing plants) and can even handle grease and animal byproducts.

Windrow composting is usually considered to be the most cost-effective composting alternative. Meanwhile, it may also have the highest fugitive emissions.

hydraulic compost turner is used in windrow composting process

Windrow composting involves long rows of compost where the actual size and shape of the windrow are dependent on the feedstocks and type of COMPOST TURNER. The piles of materials are placed in long rows, and turned by mechanical equipment to maintain optimum conditions. Mechanical turning is usually done with a full hydraulic crawler type turner machine specially designed for turning windrows. Reason of periodically turning the piles is to ensure adequate oxygen flow to the pile.
Windrow composting involves a few major steps: Feedstock Preparation, Windrow Processing and, Screening.

Feedstock preparation

–Collection: Organic waste such as green materials and food materials are recyclable through composting. Therefore, collection becomes the first step for the normal operation of industrial-scale composting facilities. Commercial and farm wastes arrive directly at the composting facility from various sources. Most of the biodegradable residuals and byproducts comes from commercial, industrial, municipal and farm/agribusiness sources. After collecting, these source-separated materials become feedstocks in a commercial composting process that turns organic waste into a valuable resource – compost.

High Moisture Fertilizer Crusher

–Size reduction: Shredding or pulverizing reduces the size of the waste articles, resulting in a uniform mass of material. Grinding the organic material before composting greatly speeds the composting process. The smaller the size of an organic refuse particle, the more quickly the microbes can consume it. It is accomplished with semi-wet materials crusher machine. Size reduction is to provide greater surface area for microbes to attack, to improve insulation, to facilitate homogenizing of initially heterogeneous material, to reduce depth for oxygen diffusion.

–Blending: Materials can be blended and mixed to achieve a suitable C/N ratio. Microbial activity is greatest when the carbon-to-nitrogen ratio (C/N) is 30:1. This can be done easily by mixing equal parts of green and brown materials. Types and volumes of feedstocks are selected to ensure the blended admixture falls within the tolerances of each parameter, ultimately coming together to meet the desired targets for C:N ratios, moisture levels, porosity and homogeneity. In order to ensure a uniform and rapid decomposition, the compost must be thoroughly mixed. Click to see compostable nitrogen-rich materials and carbon-rich wastes

Windrow processing

Windrow composting, employing long narrow windrows mechanically turned by a commercial compost turner on a regular basis, has become the most popular industrial composting method in the world, especially in developed countries such as United States, Australia, Italy etc.

commercial compost turner in operation–windrow composting facility

▼ After crushing and blending, the material to be composted is placed into windrows, in the open air. Usually dimensions of the windrow ranging from 3-12 feed tall and 8-20 feed wide, as long as it could be. The moisture content should be 45-55 percent since poor aeration occurs at higher moisture contents and slow digestion is encountered at lower moisture contents.

▼ Rows are regularly turned to make sure there is enough oxygen for the microbes to work. Frequent turning is the best way to improve compost quality, to promote high concentrations of beneficial microbes, to prevent excessively high temperatures and to ensure optimum oxygen concentrations. There are many parameters affecting the frequency of windrow turning:

—The size of the composting material and the type of composting structure also affects the frequency of turning.

—If C:N ratio these two conditions are at an ideal level and mixed well, expect less frequency of turning.

—Turning frequency should normally be based on temperature, and should occur whenever temperatures exceed to 140°F, or drop below 90°F.

▼It is considered finished when the organic material has fully decomposed and reached a stable state.

Outdoor composting in piles that rely on mechanical aeration, typically with a compost windrow turner, to optimize the composting process. Allance compost turner machines are very efficient, which makes the whole composting process fast, high-rate, and capable of rapid degradation and stabilization of almost all organic materials.

Grinding and screening of the final compost product

The final step is high speed grinding, using chain crusher.

The screening process is to remove non-compostable material from the generated compost, and to produce a finer product that meets the requirements of consumers.